Over two-thirds of the Earth is covered with salt water, and there is a relatively unlimited supply of solar energy. On the other hand, it is becoming clear that access to fresh water will be one of the biggest challenges for humanity in the twenty-first century. Unfortunately, in many areas of the world there is limited access to fresh water sources. In some instances, the lack of access can be attributed to a lack of electricity and power to filter water effectively. Poor areas, for example, typically cannot afford the costs required for installing infrastructure for electricity.